Ultraviolet Photo-Activated NO2 Gas Sensors Based on P-Type Gold-Black Nanoparticles/N-Type Ga2O3 Nanorods Grown on Nanoimprinted SnO2 Seed Layer

This study aimed to enhance the sensing performance of nitrogen dioxide (NO2) gas sensors fabricated using gallium oxide (Ga2O3) nanorod sensing membranes. The hydrothermal synthesis method was used to grow GaOOH nanorods on a roughened tin oxide (SnO2) seed layer with various periods fabricated using a nanoimprint system. Then, the GaOOH nanorods were converted to Ga2O3 nanorods by nitrogen annealing treatment. Under 10 ppm NO2 and operating temperature of 210 °C, the optimal response of the NO2 gas sensors using Ga2O3 nanorods grown on an 800 nm periodic seed layer was 56.2. To further improve the performance attributed to the spillover effect of noble metal, p-type gold-black nanoparticles (NPs) were deposited onto the n-type Ga2O3 nanorod surfaces using a vapor cooling condensation system to form p-n heterojunctions. When Ga2O3 nanorods were decorated with 1.02 at.% gold content, the optimal response was increased to 143.9 under 10 ppm NO2 at an operating temperature of 180 °C. To investigate the photo-activation effect on the NO2 gas sensors, 245 nm UV light was applied to the devices. Under the UV light intensity of 4.8 mW/cm2, the response of the resulting NO2 gas sensors without and with gold-black NPs was increased to 123.1 and 370.5, respectively.